Since you have just a standard HHR with a 2.2L I would tend to stick to the stock reccomendations for tire pressures unless you are carrying a larger load around.

Look at it this way,

Stock 215/55R/16 is 30lb. Psi Cold ...all around.

1. That brings up the first question ... What is Cold??
If you live in an area that has extremes between seasons you may want to reset your cold pressures at least twice a year.
Where I live the temps run from 75 high to 15 low as a rule. With that range your tire pressure can vary approx. 4-5 psi.

2. That being said, your standard setting is 30lb psi cold front and rear for
"Standard Load" 215/55R/16 tires.

3. You now have changed the PSI requirement by installing 225/55R/16 tires.

Because the carrying capacity of the 225's is higher you do not need as much air pressure to carry the same load.
I am assuming these are "Standard Load" tires.

You could figure it out mathematically if you have the gross weight front and rear on your HHR, but really I would make it easy on yourself and just wing it while watching carefully the tire wear pattern to see if you are wearing more on the shoulders or the center as you put on the mileage.
My best guess would be to put in 28-29 cold and go from there.
If you start too low you will have problems with your TMPS settings.

In my case I seldom carry anything of substance in the rear of the HHR so I set my rear pressure 2lbs lower then the front.
I personally like a softer ride, but really find no problem with normal driving performance and these psi settings.
Make sure you have an Accurate Gauge to check pressures and always use the same gauge each time if possible.

SF

 

I run 32 psi cold as in not driven since parked the night before. I got great even wear from my last 2 sets of tires, just my .02 cents

 

In my experiences with the HHR and different size tires and many years in the tire biz. I personally would recommend 32-34 in the front and 30-32 in the rear. Rotate every 6-8K miles and cross the rears to the front everytime (Unless they are directional). Most big name tire joints will perform this service for free. Hope this helps.

 

Thanks for all of the great input. I dropped the pressure down last night to 34 psi all the way around. It is a softer ride now but another question comes up.

I periodically check my displays to keep an eye on water temps, etc. When I got to the tire pressure readings the drivers front and passenger rear showed 37 psi each and the the other 2 still showed 34.
I know the DIC is not an accurate reading sometimes but what would make 2 tires on opposite corners heat up/pressurize more than the other 2? It was an overcast day so the sun was not heating them up. Should I be worried about the alignment or am I just being paranoid? If I am being paranoid just tell me. Its o.k., we are all friends. I can take it.

P.S. I had it aligned at the same time the tires were installed.

 

I would do a double check to see if there is also that difference with your tire gauge.

Do it cold when you are sure there has been no external heat hit any of the tires.
Then do it again immediatly after driving the car on the hiway for a while.
If there is a separate cause it should show up then.


I do not trust the TMPS and DIC for accurate measurements.
Just use as a reference only in case there is a real problem.

SF

 

I have had goodyear eagle gt's since
end of september and have around
10,404 miles on them. The ones placed
in the front i ran some where round 7,000
miles b4 rotating ( yea i know little late).
I use my HHr to deliver news papers and
i wear the outer shoulder like crazy.
eagle gt's you can still see the tread pattern
, though its worn but its visible usually that is
the 1st that is gone. The fronts are now in the
back and doing fine. These maybe the 1st tires
i repeat purchasing for my delivery vehicle ~

 

I went to America's tires and those guys told me that a 245/40/18 can be a problem because the rim tends to move inside the tire. Is that true??

 

Never heard of such a thing, They are doing a great job.

The other one has 255x40's bet he will say you can't do that either, I heard that from a place I used to buy tires.

 

O.K. the weather has been nice. It was about 75 degree around here yesterday so I decided to do a little cleaning and detailing to the ol girl. Here are a few pics of her with her new shoes. I cleaned and painted the rear drums and front disks and calipers. I still need to figure out something for the center caps. Oh, and she does still need a clay bar, polish and wax.



She has 90,500 miles on her and I enjoy her more now than the day I brought her home. Hopefully running boards and one of those fancy leather booted shifters are my next mods.

 

Looks like new, only better with the mods..